The proposed investigation is designed to gain insight into the mechanism by which two s-triazine herbicides are metabolized to derivatives which are mutagenic in prokaryote and mammalian cell test systems. We will survey metabolites of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), cyprazine (2-chloro-4-cyclopropylamino-6-isopropylamino-s-triazine) and their hydroxy derivatives, generated in vitro by maize, mammalian cells in culture, and rat liver systems to determine which system is most efficient in mutagen production by testing extracts on Salmonella strains. The metabolizing system which provides the most enriched preparation of mutagens will then be used to prepare radioactive derivatives of the appropriate ring labeled substrate. High pressure liquid chromatography will be used to isolate preparative amounts of mutagen(s), after we have determined which peak(s) of radioactivity cause reversion in the Ames' Salmonella strains. We will then determine the structure of the mutagen(s) by mass spectroscopy and study its genetic toxicology on Chinese Hamster Ovary cells using induction of mutation to 6-thioguanine resistance as the genetic marker. Finally, we propose to study the mechanism of mutagen(s) interaction with DNA to determine whether it acts as an alkylating agent, forms covalent adducts, intercalates and/or acts as a base analogue. In addition to providing information concerning the genetic toxicology of herbicides used extensively in our environment, these experiments should also bear on fundamental questions concerning the metabolism, mutagenicity and mechanism of interaction of small molecules with DNA.